1 November 1996

Sclerotina danger signs up ahead

WIDESPREAD sclerotinia infection of potatoes this season spells danger for more susceptible crops grown later in the rotation.

A larger than normal soil-borne reservoir of disease is likely, which could result in serious attacks in future seasons.

So says Paul Dover, agronomist at ADAS Huntingdon. He reckons sclerotinia is easy to find in East Anglia. Peter Gladders, plant pathologist at ADAS Boxworth, has also seen more sclerotinia in fenland crops than recent seasons.

Late spore production is to blame. "It appears there was considerably more sclerotinia about in August this year," says Dr Gladders. That proved ideal for potato infection.

Sclerotia are produced, which are returned to the soil and lie dormant. If buried, they can last up to 10 years, awaiting suitable conditions to fruit. If that occurs in a susceptible crop, damage can occur.

Most non-cereal crops are affected, explains Dr Gladders. Lettuce is probably the most susceptible in terms of economic damage. Other vegetables, carrots and sugar beet, as well as oilseed rape, can also suffer.

Growers should plan strategies accordingly, he maintains. Minimum tillage keeps sclerotia near the surface, encouraging them to germinate the following year. They then die.

Minimum tilling is difficult after potatoes, and lifting the crop may be enough to bury sclerotia, he points out. However, ploughing the following year should bring most sclerotia nearer the surface. Most will then germinate and, provided a non-host crop is planted, reduce the burden.

Once the field is planted with a susceptible crop, growers should monitor for fruiting bodies and time sprays accordingly.n